Commercial light fixtures for high ceilinged buildings, such as warehouses, gymnasiums, airplane hangars and the like, in recent years typically have used high intensity discharge (HID) lamp fixtures. Such fixtures use mercury vapor, metal halide, and high or low pressure sodium lamps, depending upon the particular application and the lighting characteristics desired. Such lamps generally are high wattage (400 or 1000 Watts, for example); so that in the building in which they are used, significant energy consumption takes place. This energy consumption translates into high utility bills.
Fluorescent lamp fixtures typically are lower wattage fixtures; but to provide the desired levels of illumination in high ceilinged buildings, many conventional fluorescent light fixtures must be used to produce the desired lumens of light on the floor of the building in which they are used. When standard fluorescent light fixtures using elongated tubes are employed, a larger number of fixtures is required to produce the same level of light produced with a smaller number of HID lamps.
HID lamps also produce an audible buzzing sound when they are operated. When large numbers of these lamps are used in a location, such as a warehouse, the hum or buzz produced by the lamps can be annoying. In addition, HID lamps of the mercury or metal halide variety utilize gas in a discharge tube, which is manufactured from quartz. Current passing through the gas generates light. The discharge tube is enclosed in an outer glass bulb. Consequently, the light passes through both the quartz discharge tube and the glass bulb. The discharge tubes of these lamps emit a high degree of ultraviolet radiation along with the light. Normally, the ultraviolet radiation is not of any consequence, since radiation in the harmful ranges is absorbed by the outer glass bulb. It is possible, however, for the outer bulb to be broken, leaving the structurally stronger quartz arc tube intact. In such an event, the HID lamp continues to burn; and ultraviolet radiation of harmful wavelengths is emitted directly, and is likely to strike persons working in or passing through the area beneath the lamp. On the other hand, light generated by fluorescent lamps contains no significant ultraviolet radiation. Although some ultraviolet radiation is produced within the fluorescent tubes, the ultraviolet radiation is absorbed by the glass tube. If the tube is broken, the lamp immediately extinguishes; and there is no danger from the damaging effect of uncontrolled ultraviolet radiation.
Generally, commercial fluorescent ceiling fixtures use fluorescent tubes having a length of four or eight feet. These tubes are placed in appropriate luminaires oriented parallel to the floor or ground to produce the desired illumination. Installation and replacement of fluorescent tubes, particularly eight-foot tubes, is somewhat difficult because of the length of the tubes involved. In addition, if the ballast in conventional fluorescent fixtures fails and needs replacement, it generally is necessary to remove the tubes from the fixture and to obtain access through the reflector area of the fixture from the bottom or light-emitting side in order to repair or replace the ballast.
Compact fluorescent tubes have been designed in a generally "folded over" configuration, which attach to a light fixture at one end. These compact folded fluorescent light tubes produce increased amounts of light for the same energy input, or the same wattage, compared with conventional elongated fluorescent light tubes.
The above identified co-pending application illustrates a lighting apparatus which employs a plurality of compact fluorescent lamps and which is designed to replace HID lamp fixtures or conventional fluorescent strip fixtures. The various reflectors of the lighting apparatus disclosed in this co-pending application have a generally bell-shaped configuration, with decreasing circular cross sections in planes parallel to the light-emitting end and proceeding toward the base or attachment end of the reflector.
It is desirable to provide a luminaire which may be substituted for HID lamps and standard multiple lamp fluorescent fixtures as direct replacements, which provides advantages of reduced power consumption, which is relatively inexpensive, which produces high lumen outputs, and which is modular in construction and easy to maintain.